Spiral curve drafting instrument



June 5, 1962 F. L. YOST 3, 37

SPIRAL CURVE DRAFTING INSTRUMENT Filed June 28, 1960 INVENTOR.

A'rraelver United States Patent 3,037,293 SPIRAL CURVE DRAFTINGINSTRUMENT Francis L. Yost, 5910 Wellesiey Ave., Pittsburgh, Pa. FiledJune 28, 1960, Ser. No. 39,326 2 Claims. (Cl. 33-174) This inventionrelates to a spiral curve drafting instrument and has for an object toprovide an improved drawing or templet aid with a precisely graduatedcurve, to be made of any suitable transparent sheet material, such as atransparent plastic, sometimes commercially known as Plexiglas and alsoby other commercial names, or other similar material, preferablyalthough not necessarily about ,1 thick and 11 /2" in diameter.

A further object of this invention is to provide a drawing aid or devicefor artists, engineers, draftsmen and architects, and others, and isgenerally intended for use when one is constructing a drawing thatrequires a curve on the drawing or plan, or on another flat surface.

A further object of this invention is to provide a drafting instrumentthat eliminates the need for the usual col lection of French curves,eliminates the need for looking over a collection of various draftinginstruments to locate a desired curve, that provides in a singleinstrument, a number of precisely graduated curves, and also provides anidentification for each portion of the curve which enables the user toreadily refer thereto and to readily locate the identical curve againwhen needed,

A further object of this invention is to provide a drafting instrumentwhich includes a plurality of spiral slotted curves therein, distinctlyidentified for ready reference, all about a central reference point,with each curve a spiral continuation of the other curve thereon, andwith an identification means generally locating the curves withinseparate quadrants, and further to provide a central point about whichthe curves are generated to enable the user to establish perpendicularsto any arc, with boundary lines between each quadrant extendingdiametrically from such central point.

With the above and related objects in view, this invention consists inthe details of construction and combination of parts, as will be morefully understood from the following description, when read inconjunction with the accompanying drawing in which:

FIG. 1 is an elevational view of the spiral curve drafting instrument ofthis invention.

FIG. 2 is a transverse sectional view on line 22 of FIG. 1.

FIG. 3 shows the generation of the spiral curve.

Referring in greater detail to the drawing wherein similar referencecharacters refer to similar parts, there is shown at 10 the spiral curvedrafting instrument of this invention comprising a body made of a thinsheet of transparent plastic material such as Plastiglas or othersimilar materials of which drafting instruments of this general natureare usually made, being preferably about 5 thick by about 11 /2" indiameter. This body is divided by boundary lines 12, 14, 16 and 18 intofour quadrants, the boundary lines stopping just short of a center pointor dot 20. This center point or dot 20 may be merely indicated on thesurface of the body 10, or, if desired, may be in the form of a smallopening through the body 10, just large enough to insert a pen or pencilpoint therethrough,

Each of the quadrants are designated A, B, C and D, and in thisdescription, such designations are also used as reference characters. Onthis body 10, a spiral curve,

Patented June 5, 1962 ICC of a desired size, is generated by winding 21tether such as a fine strand of piano wire 28 about a steel shaft 30 A"in diameter at E, coil-fashion counterclockwise, placing the shaft 30 atthe center 20, attaching a marking device 32 on the end of the Wire, themarking device 32 being maintained parallel to the shaft. With the wire28 held taut, the marking device 32 is moved in a constantly increasingradius R creating a steadily increasing breadth of arc. The same spiralused in generating the slot curves is continued to generate a spiralperiphery curve A1, be ginning at 22 at quadrant A continuing at B1, C1and through D1 ending at 24 in quadrant D, and the two ends 22 and 24 ofthe spiral periphery curve are joined by a smooth reverse S curve 26. Ofcourse, the curvature of the arc may be changed by using a differentsize shaft.

Then, when the desired spiral has been established, the body will beslotted as shown, keeping all but the innermost slot within a particularquadrant as defined by the boundary lines 12, 14, 16 and 18, theinnermost slot extending through two adjacent quadrants. The peripheralor edge curve in each quadrant is designated by the numeral 1, the nextcurve by 2, the third by 3, the fourth by 4 and the fifth by 5.

By combining the quadrant designation with the curve designation, eachcurve portion has its individual designation, such as Al, the outercurved edge in quadrant A, or such as C3, the third curved edge inquadrant C, etc. Thus every curve portion is individually identified,and when a curve is penciled on a drawing or plan, the curve portiondesignation may be temporarily penciled adjacent thereto, so that whenit is inked later on, the same curve may be used therefor.

Although this invention has been described in considerable detail, suchdescription is intended as being illustrative rather than limiting,since the invention may be variously embodied, and the scope of theinvention is to be determined as claimed.

Having thus set forth and disclosed the nature of this invention, Whatis claimed is:

1. A drafting aid template comprising a body of transparent stock havingcompletely flat parallel upper and lower surfaces, said body having aperiphery provided by a spiral curve extending almost completely aboutits peripheral edge and joined at its adjacent ends by a re verse Scurve, said spiral curve having a multiplicity of convolutionscontinuing through slightly spaced apart slots in said body to adjacenta center point about which the spiral curve is generated, eachconvolution of said spiral, beyond the innermost one, being divided intoquadrants by spirally spaced apart slots by radially aligned integralbody portions, and quadrant boundary lines extending across saidintegral body portions from adjacent,

said central point toward the peripheral edge of said body.

2. The drafting aid template of claim 1, and alphabet indiciaidentifying each quadrant, and numerical indicia correspondinglyidentifying each curve portion in each quadrant.

References Cited in the file of this patent UNITED STATES PATENTS486,699 Davis Nov. 22, 1892 2,478,071 Agrillo Aug. Q, 1949 2,500,873Sager Mar. 14, 1950 2,607,118 Debs Aug. 19, 1952 2,933,818 Palmer Apr.26, 1960

